1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_FORTIFY_STRING_H_
3#define _LINUX_FORTIFY_STRING_H_
4
5#include <linux/bitfield.h>
6#include <linux/bug.h>
7#include <linux/const.h>
8#include <linux/limits.h>
9
10#define __FORTIFY_INLINE extern __always_inline __gnu_inline __overloadable
11#define __RENAME(x) __asm__(#x)
12
13#define FORTIFY_REASON_DIR(r) FIELD_GET(BIT(0), r)
14#define FORTIFY_REASON_FUNC(r) FIELD_GET(GENMASK(7, 1), r)
15#define FORTIFY_REASON(func, write) (FIELD_PREP(BIT(0), write) | \
16 FIELD_PREP(GENMASK(7, 1), func))
17
18#ifndef fortify_panic
19# define fortify_panic(func, write, avail, size, retfail) \
20 __fortify_panic(FORTIFY_REASON(func, write), avail, size)
21#endif
22
23#define FORTIFY_READ 0
24#define FORTIFY_WRITE 1
25
26#define EACH_FORTIFY_FUNC(macro) \
27 macro(strncpy), \
28 macro(strnlen), \
29 macro(strlen), \
30 macro(strscpy), \
31 macro(strlcat), \
32 macro(strcat), \
33 macro(strncat), \
34 macro(memset), \
35 macro(memcpy), \
36 macro(memmove), \
37 macro(memscan), \
38 macro(memcmp), \
39 macro(memchr), \
40 macro(memchr_inv), \
41 macro(kmemdup), \
42 macro(strcpy), \
43 macro(UNKNOWN),
44
45#define MAKE_FORTIFY_FUNC(func) FORTIFY_FUNC_##func
46
47enum fortify_func {
48 EACH_FORTIFY_FUNC(MAKE_FORTIFY_FUNC)
49};
50
51void __fortify_report(const u8 reason, const size_t avail, const size_t size);
52void __fortify_panic(const u8 reason, const size_t avail, const size_t size) __cold __noreturn;
53void __read_overflow(void) __compiletime_error("detected read beyond size of object (1st parameter)");
54void __read_overflow2(void) __compiletime_error("detected read beyond size of object (2nd parameter)");
55void __read_overflow2_field(size_t avail, size_t wanted) __compiletime_warning("detected read beyond size of field (2nd parameter); maybe use struct_group()?");
56void __write_overflow(void) __compiletime_error("detected write beyond size of object (1st parameter)");
57void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("detected write beyond size of field (1st parameter); maybe use struct_group()?");
58
59#define __compiletime_strlen(p) \
60({ \
61 char *__p = (char *)(p); \
62 size_t __ret = SIZE_MAX; \
63 const size_t __p_size = __member_size(p); \
64 if (__p_size != SIZE_MAX && \
65 __builtin_constant_p(*__p)) { \
66 size_t __p_len = __p_size - 1; \
67 if (__builtin_constant_p(__p[__p_len]) && \
68 __p[__p_len] == '\0') \
69 __ret = __builtin_strlen(__p); \
70 } \
71 __ret; \
72})
73
74#if defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)
75extern void *__underlying_memchr(const void *p, int c, __kernel_size_t size) __RENAME(memchr);
76extern int __underlying_memcmp(const void *p, const void *q, __kernel_size_t size) __RENAME(memcmp);
77extern void *__underlying_memcpy(void *p, const void *q, __kernel_size_t size) __RENAME(memcpy);
78extern void *__underlying_memmove(void *p, const void *q, __kernel_size_t size) __RENAME(memmove);
79extern void *__underlying_memset(void *p, int c, __kernel_size_t size) __RENAME(memset);
80extern char *__underlying_strcat(char *p, const char *q) __RENAME(strcat);
81extern char *__underlying_strcpy(char *p, const char *q) __RENAME(strcpy);
82extern __kernel_size_t __underlying_strlen(const char *p) __RENAME(strlen);
83extern char *__underlying_strncat(char *p, const char *q, __kernel_size_t count) __RENAME(strncat);
84extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size) __RENAME(strncpy);
85#else
86
87#if defined(__SANITIZE_MEMORY__)
88/*
89 * For KMSAN builds all memcpy/memset/memmove calls should be replaced by the
90 * corresponding __msan_XXX functions.
91 */
92#include <linux/kmsan_string.h>
93#define __underlying_memcpy __msan_memcpy
94#define __underlying_memmove __msan_memmove
95#define __underlying_memset __msan_memset
96#else
97#define __underlying_memcpy __builtin_memcpy
98#define __underlying_memmove __builtin_memmove
99#define __underlying_memset __builtin_memset
100#endif
101
102#define __underlying_memchr __builtin_memchr
103#define __underlying_memcmp __builtin_memcmp
104#define __underlying_strcat __builtin_strcat
105#define __underlying_strcpy __builtin_strcpy
106#define __underlying_strlen __builtin_strlen
107#define __underlying_strncat __builtin_strncat
108#define __underlying_strncpy __builtin_strncpy
109#endif
110
111/**
112 * unsafe_memcpy - memcpy implementation with no FORTIFY bounds checking
113 *
114 * @dst: Destination memory address to write to
115 * @src: Source memory address to read from
116 * @bytes: How many bytes to write to @dst from @src
117 * @justification: Free-form text or comment describing why the use is needed
118 *
119 * This should be used for corner cases where the compiler cannot do the
120 * right thing, or during transitions between APIs, etc. It should be used
121 * very rarely, and includes a place for justification detailing where bounds
122 * checking has happened, and why existing solutions cannot be employed.
123 */
124#define unsafe_memcpy(dst, src, bytes, justification) \
125 __underlying_memcpy(dst, src, bytes)
126
127/*
128 * Clang's use of __builtin_*object_size() within inlines needs hinting via
129 * __pass_*object_size(). The preference is to only ever use type 1 (member
130 * size, rather than struct size), but there remain some stragglers using
131 * type 0 that will be converted in the future.
132 */
133#if __has_builtin(__builtin_dynamic_object_size)
134#define POS __pass_dynamic_object_size(1)
135#define POS0 __pass_dynamic_object_size(0)
136#else
137#define POS __pass_object_size(1)
138#define POS0 __pass_object_size(0)
139#endif
140
141#define __compiletime_lessthan(bounds, length) ( \
142 __builtin_constant_p((bounds) < (length)) && \
143 (bounds) < (length) \
144)
145
146/**
147 * strncpy - Copy a string to memory with non-guaranteed NUL padding
148 *
149 * @p: pointer to destination of copy
150 * @q: pointer to NUL-terminated source string to copy
151 * @size: bytes to write at @p
152 *
153 * If strlen(@q) >= @size, the copy of @q will stop after @size bytes,
154 * and @p will NOT be NUL-terminated
155 *
156 * If strlen(@q) < @size, following the copy of @q, trailing NUL bytes
157 * will be written to @p until @size total bytes have been written.
158 *
159 * Do not use this function. While FORTIFY_SOURCE tries to avoid
160 * over-reads of @q, it cannot defend against writing unterminated
161 * results to @p. Using strncpy() remains ambiguous and fragile.
162 * Instead, please choose an alternative, so that the expectation
163 * of @p's contents is unambiguous:
164 *
165 * +--------------------+--------------------+------------+
166 * | **p** needs to be: | padded to **size** | not padded |
167 * +====================+====================+============+
168 * | NUL-terminated | strscpy_pad() | strscpy() |
169 * +--------------------+--------------------+------------+
170 * | not NUL-terminated | strtomem_pad() | strtomem() |
171 * +--------------------+--------------------+------------+
172 *
173 * Note strscpy*()'s differing return values for detecting truncation,
174 * and strtomem*()'s expectation that the destination is marked with
175 * __nonstring when it is a character array.
176 *
177 */
178__FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3)
179char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
180{
181 const size_t p_size = __member_size(p);
182
183 if (__compiletime_lessthan(p_size, size))
184 __write_overflow();
185 if (p_size < size)
186 fortify_panic(FORTIFY_FUNC_strncpy, FORTIFY_WRITE, p_size, size, p);
187 return __underlying_strncpy(p, q, size);
188}
189
190extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
191/**
192 * strnlen - Return bounded count of characters in a NUL-terminated string
193 *
194 * @p: pointer to NUL-terminated string to count.
195 * @maxlen: maximum number of characters to count.
196 *
197 * Returns number of characters in @p (NOT including the final NUL), or
198 * @maxlen, if no NUL has been found up to there.
199 *
200 */
201__FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen)
202{
203 const size_t p_size = __member_size(p);
204 const size_t p_len = __compiletime_strlen(p);
205 size_t ret;
206
207 /* We can take compile-time actions when maxlen is const. */
208 if (__builtin_constant_p(maxlen) && p_len != SIZE_MAX) {
209 /* If p is const, we can use its compile-time-known len. */
210 if (maxlen >= p_size)
211 return p_len;
212 }
213
214 /* Do not check characters beyond the end of p. */
215 ret = __real_strnlen(p, maxlen < p_size ? maxlen : p_size);
216 if (p_size <= ret && maxlen != ret)
217 fortify_panic(FORTIFY_FUNC_strnlen, FORTIFY_READ, p_size, ret + 1, ret);
218 return ret;
219}
220
221/*
222 * Defined after fortified strnlen to reuse it. However, it must still be
223 * possible for strlen() to be used on compile-time strings for use in
224 * static initializers (i.e. as a constant expression).
225 */
226/**
227 * strlen - Return count of characters in a NUL-terminated string
228 *
229 * @p: pointer to NUL-terminated string to count.
230 *
231 * Do not use this function unless the string length is known at
232 * compile-time. When @p is unterminated, this function may crash
233 * or return unexpected counts that could lead to memory content
234 * exposures. Prefer strnlen().
235 *
236 * Returns number of characters in @p (NOT including the final NUL).
237 *
238 */
239#define strlen(p) \
240 __builtin_choose_expr(__is_constexpr(__builtin_strlen(p)), \
241 __builtin_strlen(p), __fortify_strlen(p))
242__FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1)
243__kernel_size_t __fortify_strlen(const char * const POS p)
244{
245 const size_t p_size = __member_size(p);
246 __kernel_size_t ret;
247
248 /* Give up if we don't know how large p is. */
249 if (p_size == SIZE_MAX)
250 return __underlying_strlen(p);
251 ret = strnlen(p, maxlen: p_size);
252 if (p_size <= ret)
253 fortify_panic(FORTIFY_FUNC_strlen, FORTIFY_READ, p_size, ret + 1, ret);
254 return ret;
255}
256
257/* Defined after fortified strnlen() to reuse it. */
258extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(sized_strscpy);
259__FORTIFY_INLINE ssize_t sized_strscpy(char * const POS p, const char * const POS q, size_t size)
260{
261 /* Use string size rather than possible enclosing struct size. */
262 const size_t p_size = __member_size(p);
263 const size_t q_size = __member_size(q);
264 size_t len;
265
266 /* If we cannot get size of p and q default to call strscpy. */
267 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
268 return __real_strscpy(p, q, size);
269
270 /*
271 * If size can be known at compile time and is greater than
272 * p_size, generate a compile time write overflow error.
273 */
274 if (__compiletime_lessthan(p_size, size))
275 __write_overflow();
276
277 /* Short-circuit for compile-time known-safe lengths. */
278 if (__compiletime_lessthan(p_size, SIZE_MAX)) {
279 len = __compiletime_strlen(q);
280
281 if (len < SIZE_MAX && __compiletime_lessthan(len, size)) {
282 __underlying_memcpy(p, q, len + 1);
283 return len;
284 }
285 }
286
287 /*
288 * This call protects from read overflow, because len will default to q
289 * length if it smaller than size.
290 */
291 len = strnlen(p: q, maxlen: size);
292 /*
293 * If len equals size, we will copy only size bytes which leads to
294 * -E2BIG being returned.
295 * Otherwise we will copy len + 1 because of the final '\O'.
296 */
297 len = len == size ? size : len + 1;
298
299 /*
300 * Generate a runtime write overflow error if len is greater than
301 * p_size.
302 */
303 if (p_size < len)
304 fortify_panic(FORTIFY_FUNC_strscpy, FORTIFY_WRITE, p_size, len, -E2BIG);
305
306 /*
307 * We can now safely call vanilla strscpy because we are protected from:
308 * 1. Read overflow thanks to call to strnlen().
309 * 2. Write overflow thanks to above ifs.
310 */
311 return __real_strscpy(p, q, len);
312}
313
314/* Defined after fortified strlen() to reuse it. */
315extern size_t __real_strlcat(char *p, const char *q, size_t avail) __RENAME(strlcat);
316/**
317 * strlcat - Append a string to an existing string
318 *
319 * @p: pointer to %NUL-terminated string to append to
320 * @q: pointer to %NUL-terminated string to append from
321 * @avail: Maximum bytes available in @p
322 *
323 * Appends %NUL-terminated string @q after the %NUL-terminated
324 * string at @p, but will not write beyond @avail bytes total,
325 * potentially truncating the copy from @q. @p will stay
326 * %NUL-terminated only if a %NUL already existed within
327 * the @avail bytes of @p. If so, the resulting number of
328 * bytes copied from @q will be at most "@avail - strlen(@p) - 1".
329 *
330 * Do not use this function. While FORTIFY_SOURCE tries to avoid
331 * read and write overflows, this is only possible when the sizes
332 * of @p and @q are known to the compiler. Prefer building the
333 * string with formatting, via scnprintf(), seq_buf, or similar.
334 *
335 * Returns total bytes that _would_ have been contained by @p
336 * regardless of truncation, similar to snprintf(). If return
337 * value is >= @avail, the string has been truncated.
338 *
339 */
340__FORTIFY_INLINE
341size_t strlcat(char * const POS p, const char * const POS q, size_t avail)
342{
343 const size_t p_size = __member_size(p);
344 const size_t q_size = __member_size(q);
345 size_t p_len, copy_len;
346 size_t actual, wanted;
347
348 /* Give up immediately if both buffer sizes are unknown. */
349 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
350 return __real_strlcat(p, q, avail);
351
352 p_len = strnlen(p, maxlen: avail);
353 copy_len = strlen(q);
354 wanted = actual = p_len + copy_len;
355
356 /* Cannot append any more: report truncation. */
357 if (avail <= p_len)
358 return wanted;
359
360 /* Give up if string is already overflowed. */
361 if (p_size <= p_len)
362 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_READ, p_size, p_len + 1, wanted);
363
364 if (actual >= avail) {
365 copy_len = avail - p_len - 1;
366 actual = p_len + copy_len;
367 }
368
369 /* Give up if copy will overflow. */
370 if (p_size <= actual)
371 fortify_panic(FORTIFY_FUNC_strlcat, FORTIFY_WRITE, p_size, actual + 1, wanted);
372 __underlying_memcpy(p + p_len, q, copy_len);
373 p[actual] = '\0';
374
375 return wanted;
376}
377
378/* Defined after fortified strlcat() to reuse it. */
379/**
380 * strcat - Append a string to an existing string
381 *
382 * @p: pointer to NUL-terminated string to append to
383 * @q: pointer to NUL-terminated source string to append from
384 *
385 * Do not use this function. While FORTIFY_SOURCE tries to avoid
386 * read and write overflows, this is only possible when the
387 * destination buffer size is known to the compiler. Prefer
388 * building the string with formatting, via scnprintf() or similar.
389 * At the very least, use strncat().
390 *
391 * Returns @p.
392 *
393 */
394__FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2)
395char *strcat(char * const POS p, const char *q)
396{
397 const size_t p_size = __member_size(p);
398 const size_t wanted = strlcat(p, q, avail: p_size);
399
400 if (p_size <= wanted)
401 fortify_panic(FORTIFY_FUNC_strcat, FORTIFY_WRITE, p_size, wanted + 1, p);
402 return p;
403}
404
405/**
406 * strncat - Append a string to an existing string
407 *
408 * @p: pointer to NUL-terminated string to append to
409 * @q: pointer to source string to append from
410 * @count: Maximum bytes to read from @q
411 *
412 * Appends at most @count bytes from @q (stopping at the first
413 * NUL byte) after the NUL-terminated string at @p. @p will be
414 * NUL-terminated.
415 *
416 * Do not use this function. While FORTIFY_SOURCE tries to avoid
417 * read and write overflows, this is only possible when the sizes
418 * of @p and @q are known to the compiler. Prefer building the
419 * string with formatting, via scnprintf() or similar.
420 *
421 * Returns @p.
422 *
423 */
424/* Defined after fortified strlen() and strnlen() to reuse them. */
425__FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3)
426char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count)
427{
428 const size_t p_size = __member_size(p);
429 const size_t q_size = __member_size(q);
430 size_t p_len, copy_len, total;
431
432 if (p_size == SIZE_MAX && q_size == SIZE_MAX)
433 return __underlying_strncat(p, q, count);
434 p_len = strlen(p);
435 copy_len = strnlen(p: q, maxlen: count);
436 total = p_len + copy_len + 1;
437 if (p_size < total)
438 fortify_panic(FORTIFY_FUNC_strncat, FORTIFY_WRITE, p_size, total, p);
439 __underlying_memcpy(p + p_len, q, copy_len);
440 p[p_len + copy_len] = '\0';
441 return p;
442}
443
444__FORTIFY_INLINE bool fortify_memset_chk(__kernel_size_t size,
445 const size_t p_size,
446 const size_t p_size_field)
447{
448 if (__builtin_constant_p(size)) {
449 /*
450 * Length argument is a constant expression, so we
451 * can perform compile-time bounds checking where
452 * buffer sizes are also known at compile time.
453 */
454
455 /* Error when size is larger than enclosing struct. */
456 if (__compiletime_lessthan(p_size_field, p_size) &&
457 __compiletime_lessthan(p_size, size))
458 __write_overflow();
459
460 /* Warn when write size is larger than dest field. */
461 if (__compiletime_lessthan(p_size_field, size))
462 __write_overflow_field(avail: p_size_field, wanted: size);
463 }
464 /*
465 * At this point, length argument may not be a constant expression,
466 * so run-time bounds checking can be done where buffer sizes are
467 * known. (This is not an "else" because the above checks may only
468 * be compile-time warnings, and we want to still warn for run-time
469 * overflows.)
470 */
471
472 /*
473 * Always stop accesses beyond the struct that contains the
474 * field, when the buffer's remaining size is known.
475 * (The SIZE_MAX test is to optimize away checks where the buffer
476 * lengths are unknown.)
477 */
478 if (p_size != SIZE_MAX && p_size < size)
479 fortify_panic(FORTIFY_FUNC_memset, FORTIFY_WRITE, p_size, size, true);
480 return false;
481}
482
483#define __fortify_memset_chk(p, c, size, p_size, p_size_field) ({ \
484 size_t __fortify_size = (size_t)(size); \
485 fortify_memset_chk(__fortify_size, p_size, p_size_field), \
486 __underlying_memset(p, c, __fortify_size); \
487})
488
489/*
490 * __struct_size() vs __member_size() must be captured here to avoid
491 * evaluating argument side-effects further into the macro layers.
492 */
493#ifndef CONFIG_KMSAN
494#define memset(p, c, s) __fortify_memset_chk(p, c, s, \
495 __struct_size(p), __member_size(p))
496#endif
497
498/*
499 * To make sure the compiler can enforce protection against buffer overflows,
500 * memcpy(), memmove(), and memset() must not be used beyond individual
501 * struct members. If you need to copy across multiple members, please use
502 * struct_group() to create a named mirror of an anonymous struct union.
503 * (e.g. see struct sk_buff.) Read overflow checking is currently only
504 * done when a write overflow is also present, or when building with W=1.
505 *
506 * Mitigation coverage matrix
507 * Bounds checking at:
508 * +-------+-------+-------+-------+
509 * | Compile time | Run time |
510 * memcpy() argument sizes: | write | read | write | read |
511 * dest source length +-------+-------+-------+-------+
512 * memcpy(known, known, constant) | y | y | n/a | n/a |
513 * memcpy(known, unknown, constant) | y | n | n/a | V |
514 * memcpy(known, known, dynamic) | n | n | B | B |
515 * memcpy(known, unknown, dynamic) | n | n | B | V |
516 * memcpy(unknown, known, constant) | n | y | V | n/a |
517 * memcpy(unknown, unknown, constant) | n | n | V | V |
518 * memcpy(unknown, known, dynamic) | n | n | V | B |
519 * memcpy(unknown, unknown, dynamic) | n | n | V | V |
520 * +-------+-------+-------+-------+
521 *
522 * y = perform deterministic compile-time bounds checking
523 * n = cannot perform deterministic compile-time bounds checking
524 * n/a = no run-time bounds checking needed since compile-time deterministic
525 * B = can perform run-time bounds checking (currently unimplemented)
526 * V = vulnerable to run-time overflow (will need refactoring to solve)
527 *
528 */
529__FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
530 const size_t p_size,
531 const size_t q_size,
532 const size_t p_size_field,
533 const size_t q_size_field,
534 const u8 func)
535{
536 if (__builtin_constant_p(size)) {
537 /*
538 * Length argument is a constant expression, so we
539 * can perform compile-time bounds checking where
540 * buffer sizes are also known at compile time.
541 */
542
543 /* Error when size is larger than enclosing struct. */
544 if (__compiletime_lessthan(p_size_field, p_size) &&
545 __compiletime_lessthan(p_size, size))
546 __write_overflow();
547 if (__compiletime_lessthan(q_size_field, q_size) &&
548 __compiletime_lessthan(q_size, size))
549 __read_overflow2();
550
551 /* Warn when write size argument larger than dest field. */
552 if (__compiletime_lessthan(p_size_field, size))
553 __write_overflow_field(avail: p_size_field, wanted: size);
554 /*
555 * Warn for source field over-read when building with W=1
556 * or when an over-write happened, so both can be fixed at
557 * the same time.
558 */
559 if ((IS_ENABLED(KBUILD_EXTRA_WARN1) ||
560 __compiletime_lessthan(p_size_field, size)) &&
561 __compiletime_lessthan(q_size_field, size))
562 __read_overflow2_field(avail: q_size_field, wanted: size);
563 }
564 /*
565 * At this point, length argument may not be a constant expression,
566 * so run-time bounds checking can be done where buffer sizes are
567 * known. (This is not an "else" because the above checks may only
568 * be compile-time warnings, and we want to still warn for run-time
569 * overflows.)
570 */
571
572 /*
573 * Always stop accesses beyond the struct that contains the
574 * field, when the buffer's remaining size is known.
575 * (The SIZE_MAX test is to optimize away checks where the buffer
576 * lengths are unknown.)
577 */
578 if (p_size != SIZE_MAX && p_size < size)
579 fortify_panic(func, FORTIFY_WRITE, p_size, size, true);
580 else if (q_size != SIZE_MAX && q_size < size)
581 fortify_panic(func, FORTIFY_READ, p_size, size, true);
582
583 /*
584 * Warn when writing beyond destination field size.
585 *
586 * We must ignore p_size_field == 0 for existing 0-element
587 * fake flexible arrays, until they are all converted to
588 * proper flexible arrays.
589 *
590 * The implementation of __builtin_*object_size() behaves
591 * like sizeof() when not directly referencing a flexible
592 * array member, which means there will be many bounds checks
593 * that will appear at run-time, without a way for them to be
594 * detected at compile-time (as can be done when the destination
595 * is specifically the flexible array member).
596 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101832
597 */
598 if (p_size_field != 0 && p_size_field != SIZE_MAX &&
599 p_size != p_size_field && p_size_field < size)
600 return true;
601
602 return false;
603}
604
605#define __fortify_memcpy_chk(p, q, size, p_size, q_size, \
606 p_size_field, q_size_field, op) ({ \
607 const size_t __fortify_size = (size_t)(size); \
608 const size_t __p_size = (p_size); \
609 const size_t __q_size = (q_size); \
610 const size_t __p_size_field = (p_size_field); \
611 const size_t __q_size_field = (q_size_field); \
612 WARN_ONCE(fortify_memcpy_chk(__fortify_size, __p_size, \
613 __q_size, __p_size_field, \
614 __q_size_field, FORTIFY_FUNC_ ##op), \
615 #op ": detected field-spanning write (size %zu) of single %s (size %zu)\n", \
616 __fortify_size, \
617 "field \"" #p "\" at " FILE_LINE, \
618 __p_size_field); \
619 __underlying_##op(p, q, __fortify_size); \
620})
621
622/*
623 * Notes about compile-time buffer size detection:
624 *
625 * With these types...
626 *
627 * struct middle {
628 * u16 a;
629 * u8 middle_buf[16];
630 * int b;
631 * };
632 * struct end {
633 * u16 a;
634 * u8 end_buf[16];
635 * };
636 * struct flex {
637 * int a;
638 * u8 flex_buf[];
639 * };
640 *
641 * void func(TYPE *ptr) { ... }
642 *
643 * Cases where destination size cannot be currently detected:
644 * - the size of ptr's object (seemingly by design, gcc & clang fail):
645 * __builtin_object_size(ptr, 1) == SIZE_MAX
646 * - the size of flexible arrays in ptr's obj (by design, dynamic size):
647 * __builtin_object_size(ptr->flex_buf, 1) == SIZE_MAX
648 * - the size of ANY array at the end of ptr's obj (gcc and clang bug):
649 * __builtin_object_size(ptr->end_buf, 1) == SIZE_MAX
650 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101836
651 *
652 * Cases where destination size is currently detected:
653 * - the size of non-array members within ptr's object:
654 * __builtin_object_size(ptr->a, 1) == 2
655 * - the size of non-flexible-array in the middle of ptr's obj:
656 * __builtin_object_size(ptr->middle_buf, 1) == 16
657 *
658 */
659
660/*
661 * __struct_size() vs __member_size() must be captured here to avoid
662 * evaluating argument side-effects further into the macro layers.
663 */
664#define memcpy(p, q, s) __fortify_memcpy_chk(p, q, s, \
665 __struct_size(p), __struct_size(q), \
666 __member_size(p), __member_size(q), \
667 memcpy)
668#define memmove(p, q, s) __fortify_memcpy_chk(p, q, s, \
669 __struct_size(p), __struct_size(q), \
670 __member_size(p), __member_size(q), \
671 memmove)
672
673extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
674__FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
675{
676 const size_t p_size = __struct_size(p);
677
678 if (__compiletime_lessthan(p_size, size))
679 __read_overflow();
680 if (p_size < size)
681 fortify_panic(FORTIFY_FUNC_memscan, FORTIFY_READ, p_size, size, NULL);
682 return __real_memscan(p, c, size);
683}
684
685__FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3)
686int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size)
687{
688 const size_t p_size = __struct_size(p);
689 const size_t q_size = __struct_size(q);
690
691 if (__builtin_constant_p(size)) {
692 if (__compiletime_lessthan(p_size, size))
693 __read_overflow();
694 if (__compiletime_lessthan(q_size, size))
695 __read_overflow2();
696 }
697 if (p_size < size)
698 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ, p_size, size, INT_MIN);
699 else if (q_size < size)
700 fortify_panic(FORTIFY_FUNC_memcmp, FORTIFY_READ, q_size, size, INT_MIN);
701 return __underlying_memcmp(p, q, size);
702}
703
704__FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3)
705void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
706{
707 const size_t p_size = __struct_size(p);
708
709 if (__compiletime_lessthan(p_size, size))
710 __read_overflow();
711 if (p_size < size)
712 fortify_panic(FORTIFY_FUNC_memchr, FORTIFY_READ, p_size, size, NULL);
713 return __underlying_memchr(p, c, size);
714}
715
716void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv);
717__FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
718{
719 const size_t p_size = __struct_size(p);
720
721 if (__compiletime_lessthan(p_size, size))
722 __read_overflow();
723 if (p_size < size)
724 fortify_panic(FORTIFY_FUNC_memchr_inv, FORTIFY_READ, p_size, size, NULL);
725 return __real_memchr_inv(s: p, c, n: size);
726}
727
728extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kmemdup)
729 __realloc_size(2);
730__FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp)
731{
732 const size_t p_size = __struct_size(p);
733
734 if (__compiletime_lessthan(p_size, size))
735 __read_overflow();
736 if (p_size < size)
737 fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ, p_size, size, NULL);
738 return __real_kmemdup(src: p, len: size, gfp);
739}
740
741/**
742 * strcpy - Copy a string into another string buffer
743 *
744 * @p: pointer to destination of copy
745 * @q: pointer to NUL-terminated source string to copy
746 *
747 * Do not use this function. While FORTIFY_SOURCE tries to avoid
748 * overflows, this is only possible when the sizes of @q and @p are
749 * known to the compiler. Prefer strscpy(), though note its different
750 * return values for detecting truncation.
751 *
752 * Returns @p.
753 *
754 */
755/* Defined after fortified strlen to reuse it. */
756__FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2)
757char *strcpy(char * const POS p, const char * const POS q)
758{
759 const size_t p_size = __member_size(p);
760 const size_t q_size = __member_size(q);
761 size_t size;
762
763 /* If neither buffer size is known, immediately give up. */
764 if (__builtin_constant_p(p_size) &&
765 __builtin_constant_p(q_size) &&
766 p_size == SIZE_MAX && q_size == SIZE_MAX)
767 return __underlying_strcpy(p, q);
768 size = strlen(q) + 1;
769 /* Compile-time check for const size overflow. */
770 if (__compiletime_lessthan(p_size, size))
771 __write_overflow();
772 /* Run-time check for dynamic size overflow. */
773 if (p_size < size)
774 fortify_panic(FORTIFY_FUNC_strcpy, FORTIFY_WRITE, p_size, size, p);
775 __underlying_memcpy(p, q, size);
776 return p;
777}
778
779/* Don't use these outside the FORITFY_SOURCE implementation */
780#undef __underlying_memchr
781#undef __underlying_memcmp
782#undef __underlying_strcat
783#undef __underlying_strcpy
784#undef __underlying_strlen
785#undef __underlying_strncat
786#undef __underlying_strncpy
787
788#undef POS
789#undef POS0
790
791#endif /* _LINUX_FORTIFY_STRING_H_ */
792

source code of linux/include/linux/fortify-string.h